Packing of thin glass sheets

ABSTRACT

Articles and methods for packing thin glass sheets are disclosed. The articles and methods include placing the glass sheets in a container at an angle with respect to the container wall. Spacers contact the glass sheets on the periphery of the sheets.

FIELD OF THE INVENTION

[0001] This invention relates to packing of thin glass sheets, and inparticular, liquid crystal display glass substrates.

BACKGROUND OF THE INVENTION

[0002] Large, thin glass sheets, such as liquid crystal display (LCD)substrates are flexible. LCD substrates typically are one square meterin area and have a thickness of less than 0.8 mm. The drive towardslarger and lighter LCD substrates has resulted in LCD substrates thatexceed one square meter in area and have a thickness less than 0.7 mm,and in some cases, less than or equal to 0.5 mm. At present, LCDsubstrates are typically packed vertically in a box made from foamedplastic. The peripheral edges of each substrate are held in the verticalgrooves on the sidewall of the box. As the length and width of thinglass sheets such as LCD sheets increase and the thickness decreases,the substrate becomes more flexible, and the glass spacing in the boxmust be increased to avoid glass damage and breakage by mutual contactdue to excess vibration during transportation. In view of theselimitations, improved methods and articles for packing thin glass sheetsfor storage and shipping that provide sufficient packing density andprevent breakage are needed.

SUMMARY

[0003] Certain embodiments of the invention relate to methods andarticles for packing thin glass sheets in a container having at leastone wall. The glass sheets are placed in the container at an angle withrespect to the wall of the container. The sheets rest against a mainsupport member, and spacers keep the sheets in a spaced apartrelationship. In certain embodiments, each spacer supports four cornersof the glass sheets, and in one particular embodiment, the spacer isframe-shaped. In certain embodiments, the container is tilted duringloading and unloading of the container so that the tilt angle of theglass sheets during loading and unloading is reduced. It is to beunderstood that both the foregoing general description and the followingdetailed description are exemplary and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004]FIG. 1 is a perspective view of a spacer used according to someembodiments of the invention;

[0005]FIG. 2 is a side view of a stack of glass sheets spaced apart bythe spacers shown in FIG. 1;

[0006]FIG. 3 is a side view of glass sheets packed in a containeraccording to one embodiment; and

[0007]FIGS. 4a and 4 b are side views of glass sheets packed incontainers according to alternative embodiments.

DETAILED DESCRIPTION

[0008] Before describing several exemplary embodiments of the invention,it is to be understood that the invention is not limited to the detailsof construction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orcarried out in various ways.

[0009] One embodiment of the invention relates to a spacer for thinglass sheets, and in particular LCD glass sheets. Referring to FIGS. 1and 2, a spacer 10 is shown that includes a main frame-shaped member 12and a cushion 14 on the surfaces of the member in contact with theglass. The spacer 14 according to the present invention supports theglass sheets at four corners. Supporting the glass sheets at fourcorners while tilting the glass sheets induces sufficient stiffness inthe glass sheets to prevent the sheets from sagging or breaking duringtransportation of the package. In the embodiment shown in FIG. 1, thecushion 14 is a continuous piece that extends around the entireperiphery of the main frame-shaped 12 member. However, according tocertain embodiments, the cushion can be placed in discrete and separatesections on the periphery of the frame-shaped member. One example of asuitable frame for a sheet of glass having dimensions of 985 mm×1300mm×0.7 mm is a frame-shaped member made from an acrylic material. Theframe shaped member has a thickness “t” of about 4 mm and a frame width“w” of between about 10 mm and 50 mm, and more preferably between about10 mm and 20 mm. The overall width and length dimensions of theframe-shaped member are selected to be approximately the same as thedimensions of the glass sheet. The frame width “w” is selected so thatthe cushion 14 contacts only a peripheral portion of the glass sheetthat is intended to be discarded. In one particularly preferredembodiment, the frame shaped member 12 has at least one end 15 in whichthe frame has a width “w” that is less than the width of the other threeends of the frame-shaped member. For example, in one embodiment, the end15 of frame shaped member may have a width “w” that is approximately thesame as the width of the cushion material. In preferred embodiments, end15 of the frame-shaped member 12 supports the glass sheets at the bottomof the container as shown in FIG. 2. The cushion material, according toone embodiment, includes a rubber tape having a thickness of betweenabout 0.2 mm and 2 mm, and preferably about 0.5 mm or less. Any softmaterial can be used for the cushion material, including, but notlimited to rubber tape, plastic tape, and foamed plastic tape such asfoamed polyethylene tape. In certain embodiments, a sufficiently rigidmaterial that also provides cushioning for the glass sheets so that theframe-shaped member provides both support and cushioning for the sheets.In other words, a single frame shaped member having cushioningproperties and sufficient rigidity to support the glass sheets in thecontainer at an angle can be used without a separate cushioning materialplaced on the frame-shaped member. Utilizing a frame and cushion ofthese dimensions, the spacing between each glass sheet is between about2 mm and 10 mm, and preferably between about 3 mm and 4 mm. The spacer10 should be made from a material that has sufficient stiffness andstrength to support a stack of glass sheets. Suitable materials,include, but are not limited to, acrylic resin, polyvinyl chloride resinand foamed plastics. FIG. 2 shows a plurality of glass sheets 16 stackedusing a plurality of spacers shown in FIG. 1.

[0010] A thinner spacer element is desirable to achieve a higher packingdensity of glass sheets, but the spacer should be thick enough so thatadjacent glass sheets do not contact each other during transportation ofthe shipping container holding the glass sheets. Accordingly, spacerthickness will depend on the size and thickness of the glass sheet andstacking parameters discussed in more detail below. The spacer shouldhave sufficient rigidity to maintain the shape of the spacer when thespacer is stacked vertically in a container.

[0011] Referring now to FIG. 3, a container 20 for shipping thin glasssheets 21 is shown. The container 20 includes at least one substantiallyvertical wall 22, a floor 24 and a cover 26. The container 20 should bemade from a material having enough mechanical strength to hold thepackaged glass sheets. As used herein, substantially vertically meansthe wall 22 is generally perpendicular to the floor 24 of the container20. A main support member 28 tilted at an angle “a” with respect one ofthe walls 22 is placed in the container. The main support member 28preferably is L-shaped and includes an upper portion 29 and a lowerportion 30. The upper portion 29 rests against the wall 22 of thecontainer 20. The main support member 28 should provide sufficientmechanical strength to hold the glass sheets and spacers in place, andmeet cleanliness requirements of packaged LCD glass sheets. According toone embodiment, the main support member 28 is made from acrylic platesreinforced with a steel frame. In preferred embodiments, the container20 holds between about 20 and 100 glass sheets and the required numberof spacers. An optional backing board (not shown) may be placed betweenthe upper portion and the first sheet of glass that leans against themain support member 28.

[0012] Although the upper portion 29 of the main support member 28 isshown as straight, the upper portion may be curved, as shown in FIGS.4a-4 b. In FIG. 4a, similar components are designated with referencenumerals and a followed by ′, and in FIG. 4b, similar components aredesignated with reference numerals followed by ″. As shown in FIG. 4a, amain support member 28′ includes a curved upper portion 29′ that allowsa higher packing density of sheets to be packed in the container 20′. Inan alternative embodiment shown in FIG. 4b, the main support member 28″may be straight and a curved backing board 31 may be used to allow ahigher packing density of sheets in the container 20″.

[0013] Referring again to FIG. 3, the major surfaces of the glass sheets21 rest upon the upper portion of the main support member 28, and theedges of the glass sheets 21 are supported by the lower portion 30 ofthe main support member 28. Spacers 10 maintain the glass sheets 21 in aspaced apart relation and contact the glass sheets only on the outerperiphery of the sheets. The stack of glass sheets 21 may be secured bya secondary support member 32 which encloses the stack of sheets in thecontainer 20. The main support member 28 and the secondary supportmember 32 when secured together form an inner package that is placed inthe container 20.

[0014] According to certain embodiments of the present invention, amethod is provided in which glass sheets and frame-shaped spacers arestacked alternately and leaned against a support member disposed at anangle “a” to a substantially vertical wall of the container. By packingthe glass sheets in this manner, each glass sheet is supported alongfour edges, and the unsupported central area of the sheet sags bygravity. The amount of sag is controlled by adjusting the tilt angle. Anoptimal level of sag can be imparted to the glass sheets so that thesheets are strained by elastic deformation and thus stiffened. When anoptimal tilt angle is selected, the glass sheets become stable againstexternal forces such as vibration and shaking during transportation. Theglass sheets are arranged in the container such that adjacent sheets arenot in contact. Referring again to FIG. 3, according to one preferredembodiment, during loading and unloading of the glass sheets, thecontainer 20 is tilted at an angle “b” with respect to the surface uponwhich the container rests, so that the tilt angle of the glass sheets isdecreased with respect to the surface upon which the container restsduring the loading and unloading steps. Typically, the surface uponwhich the container rests is a horizontal surface, and tilting of thebox in this manner facilitates loading and unloading of the sheetsbecause the sheets can be loaded in the container in a substantiallyvertical orientation with respect to the lower portion of the mainsupport member. In preferred embodiments, during transportation andstorage of the container, the angle “b” of the container with respect tothe surface upon which the container rests is reduced so that the bottomsurface of the box lies flat on the supporting surface.

[0015] A test was conducted to determine the optimum tilt angle andspacing of glass sheets in a container. Glass sheets having a thicknessof about 0.7 mm and dimensions of about 985 mm×1300 mm were loaded in asupport member of the type shown in FIG. 3 with acrylic frame shapedspacers 3 mm thick in contact with the periphery of the sheet. Thespacer also included 0.5 mm of cushion (rubber tape) around theframe-shaped spacer, providing a total thickness of about 4 mm. Fiveglass sheets and six spacers were placed in a container, and nosecondary support member was placed in the container. The amount of sagwas measured at the center of the glass sheet using either calipers or alaser distance meter. The sag values at various angles are reported inTable I.

[0016] A secondary support was placed in the container as shown in FIG.3, and the secondary support member and support member were tiedtogether firmly. The stack of glass sheets tied between the supportmembers was shaken back and forth in the direction shown by arrow 40 inFIG. 3. Glass stiffness was observed at different tilt angles, and theobservations are reported in Table I. As indicated in Table I, the glasssheets become sufficiently stiff when the angle “a” between the upperportion of the main support member and the wall is about 20 degrees.TABLE I Angle “a” Sag (mm) Stiffness Observation Upon Shaking 0 0Flexible, rattled easily. 5 2.0 Flexible, rattled easily. 10 2.5Increase in stiffness and decrease in rattle. 15 3.0 Increase instiffness and decrease in rattle. 20 3.5 Nearly stiff; no rattle 25 4.0Sufficiently stiff; no rattle. 30 4.5 Sufficiently stiff; no rattle.

[0017] The packaging method described above has also been successfullyapplied to LCD substrates having dimensions of about 1500 mm×1800 mm×0.7mm. Twenty glass sheets and twenty-one spacers were alternately placedin a boxed tilted 5 degrees. The box was made of acrylic platesreinforced with a steel frame. The spacers were made from an acrylicmaterial having a thickness of about 3 mm and a cushion made from foamedpolyethylene tape having a thickness of about 0.5 mm or less. Thestacked glass sheets and spacers were tied together firmly, and thenlifted at an angle of between about 5 degrees and 30 degrees. As thetilt angle increased, the glass deformed more by gravity sag, and wasmore stabilized against mechanical vibration. The optimum tilt anglewill be determined by further experiments measuring the expectedexternal vibration during package transportation.

[0018] The various embodiments of the invention are particularly usefulfor storing and shipping LCD glass substrates having an area greaterthan one square meter. As discussed above, these glass sheets typicallyhave a thickness less than about 0.8 mm, and some sheets have athickness less than or equal to about 0.5 mm. The present invention hasbeen successfully demonstrated on LCD substrates having dimensions ofabout 1500 mm×1800 mm×0.7 mm. The front and back major surfaces of theglass sheet are not contacted by the spacers, except for a peripheralportion of the sheet which typically discarded by the end user. No filmsor surface coatings are required on the glass sheets to preventscratching, reducing the cost of processing of the glass sheets.Handling of the glass sheets is simplified and loading and unloading ofthe shipping container is simple and requires no special equipment.According to certain embodiments of the present invention the glasssheets packed in containers are stiffened by the gravitational forceinduced when the sheets are packed at an angle in a package. Thestiffening reduces the glass flexibility and reduces the chance of glassbreakage due to external vibration during transportation.

[0019] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover modifications and variationsof this invention provided they come within the scope of the appendedclaims and their equivalents.

What is claimed is:
 1. A package for thin glass sheets comprising: atleast one substantially vertical wall and a substantially horizontalfloor; a main support member tilted at an angle with respect to thewall; and a plurality of spacers adapted to separate the glass sheets bycontacting the sheets on the peripheral edges of the sheets, each spacersupporting at least one glass sheet at four corners of the sheet.
 2. Thepackage of claim 1, wherein the glass sheets are liquid crystal displaysubstrates.
 3. The package of claim 2, wherein the glass sheets have athickness less than about 0.8 mm.
 4. The package of claim 3, wherein theglass sheets have a thickness less than equal to about 0.5 mm.
 5. Thepackage of claim 1, wherein the angle between the wall and a portion ofthe main support member is greater than about 5 degrees.
 6. The packageof claim 1, wherein the angle between the wall and a portion of the mainsupport member is greater than or equal to about 20 degrees.
 7. Thepackage of claim 1, wherein the angle between the wall and a portion ofthe main support member is between about 15 degrees and 30 degrees. 8.The package of claim 1, wherein spacer has a thickness less than about 5mm.
 9. The package of claim 8, wherein the spacer is in the shape of aflexible frame that contacts the glass sheets only on the peripheraledges of the sheets.
 10. The package of claim 9, wherein the spacerincludes a main frame made from acrylic material and an auxiliarycushion material associated with the main frame.
 11. The package ofclaim 1, wherein the main support member is L-shaped including an upperportion for supporting a major surface of the glass sheets and a lowerportion for supporting the edges of the glass sheets.
 12. The package ofclaim 12, wherein the upper portion of the main support member iscurved.
 13. A method of packaging thin glass sheets comprising:providing a container having a substantially vertical wall and asubstantially horizontal floor; disposing a portion of the main supportmember in the container at an angle with respect to the wall; separatingthe glass sheets with a frame-shaped spacer; and placing the glasssheets in the container so that the glass sheets rest on the mainsupport member in a spaced apart relation and each spacer supports atleast one glass sheet at four corners of the sheet.
 14. The method ofclaim 13, further comprising placing spacers between the glass sheets,wherein the spacers contact only the periphery of the glass sheets. 15.The method of claim 13, wherein the glass sheets have a thickness ofless than about 0.8 mm.
 16. The method of claim 15, wherein the anglebetween a portion of the main support member and the wall is less thanabout 30 degrees and greater than about 5 degrees.
 17. The method ofclaim 15, wherein the angle between a portion of the main support memberand the wall is less than about 20 degrees and greater than about 5degrees.
 18. The method of claim 15, wherein the angle between a portionof the main support member and the wall is between about 15 degrees and30 degrees.
 19. The method of claim 14, wherein the spacer includes aflexible acrylic frame and a cushioning element associated with theframe.
 20. The method of claim 19, wherein the frame has a width ofbetween about 10 mm and 20 mm.
 21. The method of claim 14, wherein themain support member is L-shaped having an upper portion for supportingthe major surface of the sheets and a lower portion for supporting theedges of the sheets.
 22. The method of claim 13, wherein during the stepof placing the sheets in the container the container is placed on ahorizontal surface and the container is tilted such that the angle ofthe sheets with respect to the horizontal surface is decreased.
 23. Themethod of claim 22, further including securing the glass sheets betweena secondary support member and the main support member so that the glasssheets are sandwiched between both support members and securing a lid onthe container.